Centrifugal separator for cold milk products and the like



H. M. SPROSS 2,668;008

CENTRIFUGAL SEPARATOR FOR cow MILK PRODUCTS AND THE LIKE 2 Sheets-Sheet l I INVENTOR ATTORNEYS a, 5/ E7 M. z a a EG- J Feb. 2, 1954 v Original Filed April 1, 1950 M. SPROSS CENTRIFUGAL SEPARATOR FOR COLD Feb. 2, 1954 2,668,008

I MILK PRODUCTS AND THE LIKE Original Filed April 1, 1950 2 Sheets-Sheet 2 f V V 0 m -C T 1 .S, H

Patented Feb. 2, 1 954 CENTRIFUGAL SEPARATOR FOR COLD MILK PRODUCTS AND THE LIKE Hubert M. Spross, Poughkcepsie, N. Y., assignor to De Laval Separator Company, Poughkeepsie, N. Y., a corporation of New Jersey 7 Original application April 1, 1950, Serial No. 153,408. Divided and this application October 7, 1952, Serial No. 313,462

3 Claims. (01.233-21i This invention relates to centrifuges for separating liquids according to their relative specific gravities, and it has for its principal object the provision of an improved centrifuge adapted especially for the continuous separation of cream from whole milk at low temperature.

This application is a division of my copending application Serial No. 153,408, filed April 1, 1950.

It has long been the general and accepted practice in dairy plants to heat milk, immediately prior to centrifugal separation, to a temperature of 90 F.-92 F. Within this temperatur range, the viscosity of the separated cream is sufficiently low to permit its exit from the centrifugal bowl without clogging due to buttering, a phenomenon well known in the art of separating whole milk into its cream and skimmilk components.

The disadvantages of milk separation within this usual and somewhat elevated temperature range are two-fold. There is the added expense for the heating equipment itself and its operation to maintain the milk at the prescribed temperature, and there is a resulting loss of casein from the skimmilk. Since some casein in the form of colloidal calcium caseinate begins to precipitate and be centrifugally separable from the whole milk at a temperature of 70 F., any heating beyond this point results in an increasing loss in valuable casein by-products manufactured from the separated skimmilk. This loss occurs because the casein is separated as a solid and collects on the bowl wall together with other separated impurity solids. When the bowl is cleaned, the separated solids are thrown away.

With the centrifuge of the present invention, the whole milk can be separated continuously at a temperature within the range of 40 F. to 50 F., and the inherent tendency of the highly viscous separated cream component to clog the bowl is overcome or, at least, greatly reduced.

A centrifuge made according to the invention comprises a stack of conical discs located in the separating chamber of a rotatable centrifugal bowl and forming thin separating spaces between the discs. The discs have central holes, and the bowl chamber has within the edges of these holes a free space which provides unobstructed communication inwardly from the discs toward the rotation axis of the bowl. In order to rotate the discs at the same speed as th bowl, means are provided outside this free space which engage the discs and form a driving connection between the bowl and the discs. The milk product is fed to the separating chamber through an axial feed pipe having an air-tight connection with the bowl, the milk product being delivered from the feed pipe through a feed passage leading to the disc stack at a region spaced outwardly from the free space within the discs. The separated light component or cream is displaced inwardly from the discs into the free space, where it passes without obstruction into a central outlet passage leading from one end of this free space. The skimmilk or heavy component separated between the discs passes to the outer part of the bowl and then into a second outlet passage. A stationary discharge pipe outside the bowl communicates with the central or cream outlet passage, and an air-tight seal is provided between the discharg pipe and the bowl to form a closed path from the free space within the discs through the central outlet passage to the discharge pipe. Preferably, the skimmilk outlet passage also communicates through an air-tight seal with a second stationary discharge pipe outside the bowl. 1

By virtue of this combination of air-tight connections with the bowl for the feed and discharge and the free space within the inner edges of the discs, the separated cream can be discharged from the bowl under pressure without clogging it, even when the separated cream component is at relatively low temperature and has a high viscosity. The sealed connections with the bowl for the feed and the discharge enable the use of a relatively high pressure at the inlet side of the bowl, and because of the absence of the usual tubular shaft, disc support, or other obstruction at the inner edges of the discs, the relatively high pressure feed of the milk product is made effective to force the separated cream from the bowl in a continuous stream. In some cases, it is advantageous to provide a branch feed passage leading from th feed pipe directly to the free space within the discs, at the end of this space opposite the central discharge outlet for the cream component, so that some of the milk product is forced under pressure into the free space with a jet action to facilitate further the discharge of the viscous cream. 7

In the preferred construction, the milk product is fed from the feed pipe into a feed chamber formed by a hollow nave in the bowl, and a hollow tube extends into the inner part of the feed chamber to form a feed passage leading to a set of distributing holes in the discslocated some distance outwardly from the free inner edges of the discs. In this way, the milk product is delivcred to the disc spaces substantially free of turbulence. Also, the discs are preferably centered in the bowl by radial wings extending inwardly from the bowl periphery and engaging the outer edges of the discs, the latter having notches for receiving the inner edge of one of the wings to provide the driving connection between the bowl and the disc stack. The wings may be formed with openings to permit circulation of the separated skimmilk in the outer part of the bowl, in the vicinity of the outlet passage for the skimmilk.

According to the present invention, the free space within the discs surrounds a tapered axial shaft which supplements the high feed pressure in discharging the viscous cream through the free space.

For a better understanding of the invention reference may be had to the accompanying drawings, in which Fig. 1 is a vertical sectional view of a preferred form of the new centrifuge; and

Fig. 2 is a horizontal sectional view on the line 2-2 in Fig. 1.

Referring to the drawings, the centrifuge comprises a bowl shell H) which supports a central hollow nave l l and is, in turn, centrally supported on and rotated by a hollow spindle 12. Within the nave H is a nut I3 for securing the bowl to the spindle. A bowl top H! is secured to the upper part of the shell by a coupling ring and forms a bowl neck Ma.

A stack of conical discs H is mounted in the separating chamber of the bowl, the discs being separated by the usual caulks (not shown) to form thin separating spaces between the discs. It will be understood that the discs are spaced closely together, although for the purpose of clarity I have omitted some of the discs in Fig. 1 of the drawings. The discs have central holes Ha, the edges of which define a free central space in a separating chamber of the bowl. That is, the central space It provides unobstructed communication from the discs ll toward the rotation axis of the bowl. Since the inner edges of the discs are free, I provide outside the central space [8 means for centering the discs in the bowl and driving them at the same speed as the bowl. Such means, as shown, comprise circumferentially spaced wings l9 welded or otherwise secured to the bowl periphery. The wings extend radially inward into engagement with the outer edges of the discs, which are formed with notches I?!) for receiving the inner edge of one of the wings l9 and thereby form a driving connection between the bowl and the disc stack.

The whole milk is fed into a central passage 12a in the spindle l 2. The upper portion of the spindle is tapered and fits closely in the bottom of the bowl. Thus, the spindle serves as an axial feed pipe having an air-tight connection with the bowl. The whole milk is delivered under pressure into the lower end of the spindle from a fixed pipe through a conventional sealed connection (not shown) such as that illustrated in Lindgren Patent No. 1,901,461. From the hollow spindle l2, the whole milk passes through openings l3a in the nut [3 into a feed chamber i la formed by the nave II. Hollow tubes extend from the wall of the nave into the inner part of the feed chamber Ha and form feed passages leading upward and outward to vertically aligned distributing holes [10 in the discs, these holes being located a short distance outward from the central free space I8.

4 central outlet passage 22a leading upward through an inner neck 2% from the central free space la. The central neck or tube 22b of the top disc extends upward into a stationary head 23 mounted on the frame of the centrifuge, and it communicates with a stationary discharge pipe 24 secured to the head. Between the discharge pipe 24 and the bowl is an air-tight seal comprising rubber rings or packings 25 closely surrounding the tube 22b and held within the stationary head 23. In this way, a closed path is provided for the separated cream from the upper end of the free central space i8 through the central outlet passage 22a to the discharge pipe 24.

The top disc 22 forms with the bowl top H! a number of passages 26 extending inwardly and upwardly from the outer zone of the separating chamber at the region of the outer edges of the discs H. The passages 26, which may be separated from each other by wings on one of the members i4 and 22, extend between the tube 221) and the neck I la, the passages opening into a space 23a in the head 23. The space 23a communicates with a fixed discharge pipe 2! for the skimmilk or heavy component. Between the dis charge pipe 2'! and the bowl is an air-tight seal comprising the rings 25 above th space 23a and a rubber packing or ring 28 below this space. The ring 28 closely surrounds the neck Ma and is secured between the head 23 and the stationary cover 29. Thus, a closed path for discharging the separated skimmilk is provided from the outer part of the separating chamber through passages 26, head 23 and discharge pipe 21, and this path is sealed from the discharge path for the cream.

The free space {Ba surrounds an axial upwardly-tapered shaft as of small diameter which is supported by and rotates with the nave ii. The shaft 38 is threaded or otherwise secured to the top of the nave and extends upwardly toward the outlet passage 22a throughout most of the vertical extent of the free space 580.. A wing 31 of the Archimedes screw type is secured to the periphery of shaft 32 and spirals upwardly around the shaft in the same direction as the rotation of the bowl. Thus, since the cream in the free space its rotates at a higher angular speed than the bowl, due to run-ahead between the cream and the bowl, the wing 3| acts to force the cream upward- 1y toward the discharge passage 22a and thereby supplement the feed pressure in expelling the cream from the bowl.

In the operation of the centrifuge, the milk product is delivered under pressure through the hollow spindle or feed pipe 12 into the distributing holes lie of the discs in the separating chamber, by way of the passages previously described. In the thin layers or spaces between the discs, the skimmilk is separated from the cream and passes outwardly to the outer zone of the bowl chamber in the region of the disc-supporting wings l9, from which it is discharged through the closed path previously described. The separated cream is displaced inwardly into the central free space It! within the disc stack. In this space, the feed pressure is eiiective to force the viscous cream upwardly into and through the closed cream path leading to discharge pipe 2 5, since the central space [8 does not obstruct the cream flow and contains only the tapered shaft 36 which assists in expelling the cream from the bowl.

It will be understood that according to the invention the centrifugal separation of cold milk (or other products in which the separated light com- Above the discs I! is a top disc 22 forming a ponent has a strong tendency to plug the bowl) is made possible by the combination of the airtight connections of the feed and discharge pipes to the bowl and the free central space l8 containing the tapered shaft 30 within the disc stack. By centering and driving the discs from the outside, instead of from the inside as in conventional designs, the highly viscous cream is forced through the central part of the bowl by the feed pump without contacting any rotating part in the space I8 other than shaft 30, so that there is no tendency to impede the action of the feed pressure in discharging the cream. It will be noted that the inner flange of each disc I! is in a horizontal plane and presents an unbroken surface to the flow of the cream component.

The disc-supporting wing I9 may be formed with holes l9a near the outlet passages 26, for circulation of the skimmilk component. Also, the rate of discharge of separated cream may be controlled by a valve system in pipe 24, as disclosed in Hapgood Patent No. 2,160,140.

While I prefer the use of the helical wing 3| on the shaft 30, this wing can be eliminated if desired. The upward taper of the shaft 30, in conjunction with the high feed pressure, serves in itself to facilitate discharge of the cream from the free space [8a.

I claim:

1. In an air-tight centrifuge, the combination of a rotatable centrifugal bowl having a separating chamber, a stack of conical discs in the chamber forming thin separating spaces between the discs, the discs having central holes and the bowl chamber having within adjacent edges of said holes a free space providing an unobstructed communication inwardly from said edges toward the rotation axis of the bowl, means outside said free space engaging the discs and forming a driving connection between the bowl and the discs, an axial feed pipe having an airtight connection with the bowl, the bowl having a feed passage communicating with said pipe for leading the feed to the disc stack at a region spaced outwardly from said free space, the bowl also having a central light component outlet passage leading from one end of said free space and a heavy component outlet passage leading from the outer part of the separating chamber, a stationary discharge pipe outside the bowl and communicating with the central outlet passage, an air-tight seal between the discharge pipe and the bowl to provide a closed path from said free space through the central outlet passage to the discharge pipe, and a tapered axial shaft mounted in the bowl and surrounded by said free space, said shaft extending throughout most of the axial extent of said free passage and tapering toward said central outlet passage, the tapered shaft forming at the inner edges of the discs an annular free space which increases gradually in cross-sectional area toward said central outlet passage.

2. The combination according to claim 1, comprising also a spiral wing on said tapered shaft and spiraling upwardly in a direction to force the light component upwardly toward said outlet passage leading from one end of said free space.

3. The combination according to claim 1, in which said free inner space extends continuously through the disc stack and continuously around said edges.

HUBERT M. SPROSS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 547,404 Springer Oct. 1, 1895 1,422,856 Hapgood July 18, 1922 1,427,486 Lindgren Aug. 29, 1922 1,916,870 Strezynski July 4, 1933 1,945,336 Strezynski Jan. 30, 1934 2,002,954 Lindgren May 28, 1935 2,089,043 Svensjo Aug. 3, 1937 2,089,122 Jones Aug. 3, 1937 2,173,580 Fawcett Sept. 19, 1939 2,222,727 Stigen Nov. 26, 1940 

